This invention relates to a teletext receiver that is capable of displaying a teletext picture in an area that is essentially one half of the display screen and of displaying another teletext picture or a normal video picture in the remaining portion of the screen without having the two pictures overlap.
In a conventional teletext receiver like a television receiver, a teletext picture can be selectively displayed on a screen alone, or the teletext picture can be superimposed on a normal video picture. In both cases, the normal video picture either cannot be seen at all or cannot be seen sufficiently when the teletext picture is displayed.
In another conventional television receiver, the normal video picture is displayed as a main picture on a full screen and the teletext picture is displayed as a picture in picture (hereinafter PIP) in a small "window" provided in the main picture or vice versa as disclosed in JP-A-1 296 878, JP-A-1 296 879, JP-A-2 228 186 and European Patent EP-A-O 489 387, U.S. Pat. No. 5,023,721 and U.S. Pat. No. 5,128,766. If the teletext picture is displayed as a PIP, it is difficult to read the text of the teletext picture due to the small size of the PIP. On the other hand, if the teletext picture is displayed as the main picture, a part of the teletext picture is covered by the "window" which displays the normal video picture and some important information may be obliterated.
It is also known from JP-A-57-206 178, JP-A-61-105190, JP-A-61-193580 and JP-A-1-276977 to split the screen vertically or horizontally into two areas: one displaying the normal video picture and the other displaying the teletext picture by controlling the deflection system of the television receiver. However, the circuit construction of such a television receiver is complicated.
For teletext transmission, normally the teletext data representing more than one page of teletext are transmitted during the vertical blanking periods in a television channel. Therefore, in a conventional teletext receiver, it is possible to store teletext data of more than one page in a teletext memory by assigning certain pages to be stored and to display more than one teletext picture on the screen at the same time by dividing the screen into more than one area as disclosed in JP-A-61-105190, JP-A-1-296878 and JP-A-1-296879. However, if the display area of the screen is split in four, for example, the size of each picture becomes too small to read.